HST type axle driving apparatus with brake and transmission interlock

ABSTRACT

An HST type axle driving apparatus for driving axles, wherein, when a braking device provided in the apparatus is operated for braking in the state of forwardly or backwardly speed changing, a hydraulic pump or a hydraulic motor at the HST speed change apparatus is subjected to an over-load, so that in order to eliminate the overload, an association mechanism is so constructed that the HST type speed change apparatus changed of the speed forwardly or backwardly is forcibly and reliable kept in the neutral when the braking device is operated. Also, the association mechanism is disposed within a transmission case so as to make the HST type axle driving apparatus compact.

FIELD OF THE INVENTION

The present invention relates to an HST (Hydro-Static Transmission) typeaxle driving apparatus which houses an HST type speed change apparatusin a transmission case for driving the axles, and more particularly to amechanism for returning a speed change operation unit at the HST typespeed change apparatus to the neutral position when a brake pedal isoperated.

DESCRIPTION OF THE PRIOR ART

Conventionally, the assembly of a variable displacement hydraulic pumpand a fixed displacement hydraulic pump for an HST type speed changeapparatus integrally in the transmission case has been well known asdisclosed in the U.S. Pat. No. 3,196,696.

In a case where a braking device at the HST type axle driving apparatusexerts the braking action, the return of the HST type speed changeapparatus to the neutral has been well known as disclosed in theJapanese Patent Laid-Open Gazette No. Sho. 59-216733.

The providing of a cam groove at an arm to operate a variable swashplate so as to slowly change rotation thereof in the vicinity of thespeed change neutral position has been well known as disclosed in theJapanese Utility Model Publication No. Sho. 48-25682 and No. Sho51-7623.

SUMMARY OF THE INVENTION

In the axle driving apparatus equipped with the HST type speed changeapparatus, when a separately attached braking device is operated in thestate where the HST type speed change apparatus changes the speedforwardly or backwardly, the HST type speed change apparatus whiledelivering pressure oil from the variable displacement hydraulic pump tothe fixed displacement hydraulic pump is forcibly applied with thebraking action, which causes an overload state, thereby creatinginconvenience such as the engine stopping, or the variable displacementhydraulic pump or the fixed displacement hydraulic pump, becomingbroken.

The present invention is characterized by including an associationmechanism which, when the braking device attached to the HST speedchange apparatus is operated to apply braking to the axles, forciblyreturns to the neutral position the variable swash plate at the variabledisplacement hydraulic pump of the HST type speed change apparatusbefore breaking is applied to the axles.

In the present invention, the HST type speed change apparatus is housedin the transmission case, whereby the association mechanism for thebraking device and variable swash plate is constructed to be compactwhen housed in the transmission case.

Other objects and aspects of the invention will become apparent from thefollowing description of embodiments with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the principal portion of a running vehicleloading thereon an HST type axle driving apparatus of the invention,

FIG. 2 is a plan view showing the interior of the HST type axle drivingapparatus of the invention,

FIG. 3 is a sectional front view of the same,

FIG. 4 is a plan view of a first embodiment of the HST type axle drivingapparatus of the invention, showing an association mechanism for abraking device provided at the external upper surface of a transmissioncase and the speed change apparatus,

FIG. 5 is a perspective view of a speed change cam plate 44 and aregulation arm 42 at the same,

FIG. 6 is a plan view of the association mechanism in the state wherethe speed change cam plate 44 is rotated to rotate a swash plate anglecontrol shaft 11,

FIG. 7 is a plan view of the association mechanism of FIG. 6 at theinitial state where the swash plate angle control shaft 11 is at theneutral position, the braking device starts the braking action, and theregulation arm 42 starts rotation,

FIG. 8 is a plan view of the association mechanism of FIG. 7 in thestate where the regulation arm 42 is rotated to the position where thebraking device exerts the braking action,

FIG. 9 is a plan view of a second embodiment of the HST type axledriving apparatus of the invention, in which the association mechanismis housed in the transmission case,

FIG. 10 shows the interior of the transmission case 1 of FIG. 9 in thestate where an upper half case 1a is removed,

FIG. 11 is a plan view of the association mechanism of the brakingdevice and speed change apparatus of FIG. 10,

FIG. 12 is a sectional side view showing the relation between a variableswash plate 12 and the swash plate angle control shaft 11 of FIG. 10,

FIG. 13 is a side view showing arrangement of a regulation arm 51 and aconnecting rod 53 of FIG. 10,

FIG. 14 is a plan view of a third embodiment of the invention,

FIG. 15 is a side view of the association mechanism of the same, and

FIG. 16 is a perspective view showing the association mechanism of FIG.14 mounted on the rear surface of the upper half case 1a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIG. 1, an HST type axle driving apparatus of the inventionattached to a tractor will be described.

An engine E disposed in a bonnet of the tractor is of a vertical crankshaft type, an output pulley 19 is fixed to the lower end of thevertical crank shaft, and a V-belt wound on the output pulley 19 iswound on an input pulley 2 at a pump shaft 6 projecting from atransmission case 1a and 1b.

Axles 13 and other shafts are supported through bearings to the junctionsurface of the transmission case constituted of an upper half case 1aand a lower half case 16, the axles 13 laterally projecting drivedriving wheels 14 respectively, and steering wheels 18 are disposedbelow the engine E.

A speed change operation unit 4 for changing the speed of the HST typeaxle driving apparatus housed in the transmission case and for drivingthe axles 13 is formed as a longitudinal footpedal; and a brake pedal 25for operating the braking device is juxtaposed with the speed changeoperation unit 4.

The brake pedal 25 is connected to a brake link 43 through a shockabsorber 23.

Referring to FIGS. 2 and 3, explanation will be given generally onconstruction of the speed change apparatus in the transmission case andthe braking device.

The axle driving apparatus that journals axles 13 at the rear portion ofthe transmission case comprising the upper and lower half cases 1a and1b, houses the HST type speed change apparatus in the front portion ofthe same, disposes a braking device at the end of the same, and disposesat the outside or the inside of the upper surface of upper half case 1aan association mechanism for the braking device and speed changeapparatus as discussed below.

The HST type speed changing apparatus for changing the number ofrotations of the axles 13 is so constructed that an oil passage plate 3of substantially L-like shape when viewed from front is fixed to thelower surface of uppper half case 1a by bolts, a pump mounting surface3b is provided at the upper surface of a horizontal plate 3a of the oilpassage plate 3, and a variable displacement hydraulic pump is mountedon the pump mounting surface 3b.

Crescent oil passages 3c and 3d are bored at the pump mounting surface3b, and a pump shaft 6 is erected at the center between the oil passages3c and 3d and projects upwardly from the upper half case 1a so as to fixan input pulley 2.

A cylinder block 7 (FIG. 3) is fitted onto the pump shaft 6, pistons 8each biased by a biasing spring 9 are fitted into the cylinder block 7and disposed around the pump shaft 6, the upper end of each piston 8abuts against a thrust bearing 10, and the thrust bearing 10 is fixedlyfitted onto a variable swash plate 12.

The upper surface in a circular arc of the variable swash plate 12 isslidably guided by the rear surface of the upper half case 1a.

The variable swash plate 12 engages at the outer wall thereof with anarm fixed to a swash plate angle control shaft 11 so that the swashplate angle control shaft 11 is rotated to horizontally rotate the arm,whereby the upper surface in circular arc slidably moves to changeinclination of variable swash plate 12 so as to change a dischargeamount of operating oil. Hence, a fixed displacement hydraulic motor Mis made variable of the rotation speed.

Also, a motor mounting surface 3i is formed at the outer surface of avertical plate 3j at the oil passage plate 3 and the fixed displacementhydraulic motor M is attached to the motor mounting surface 3i.

In other words, crescent oil passages 3m and 3n are bored at the motormounting surface 3i, which communicate with the crescent oil passages 3cand 3d through horizontal oil passages 3e and 3f provided in parallel tothe horizontal plate 3a respectively.

A motor shaft 5 projects from the center of the motor mounting surface3i in parallel to the axles 13, a cylinder block 20 is fitted onto themotor shaft 5, each piston 22 biased by a biased spring 21 is fittedinto the piston 22, and a fixed thrust bearing 24 abuts against theutmost end of each piston 22.

Accordingly, when the pump shaft 6 together with the cylinder block 7 isrotated, for example, pressure oil generated at the crescent oil passage3c passes the horizontal oil passage 3e and is guided to the crescentoil passage 3m and then drives the motor shaft 5 together with thecylinder block 20. Thereafter, the pressure oil is discharged from thecrescent oil passage 3n, passes the horizontal oil passage 3f, and istaken in the cylinder block 7 from the crescent oil passage 3d.

The other ends of the horizontal oil passages 3e and 3f are closed bycheck valves 15 and 16 respectively. The check valves 15 and 16 areoperated from the exterior to allow the horizontal oil passages 3e and3f to communicate with the tank so as to make rotatable the fixeddisplacement hydraulic motor M. An oil filter 17 is disposed below thecheck valves 15 and 16 so that lubricating oil in the transmission case1 is supplied as operating oil to the HST type speed change apparatus byopening the check valves 15 and 16.

An output gear 5a is provided on the motor shaft 5 and engages with alarge diameter gear 27 on a counter gear 26 and a toothed gear 26a onthe counter shaft 26 engages with a differential ring gear 28, so that adriving force from the motor shaft 5 is transmitted to the axles 13through a differential gear unit.

A brake drum 29 is fixed to the utmost end of the motor shaft 5 and abrake lever 30 pivoted to a lid 31 fixed to the side surface of thetransmission case 1 is turned, whereby brake shoes in the brake drum 29are expanded to exert the braking action.

Next, explanation will be given on a first embodiment of the inventionshown in FIGS. 4 through 8.

The brake lever 30 is pivotally connected with a brake link 33, theother end thereof is pivotally connected to one end of a bell crank 34,which is pivotally supported at an intermediate portion to a pivot shaft36 projecting from the transmission case 1, and the other end of bellcrank 34 is pivotally connected with a shock absorber 35.

The shock absorber 35 is provided in order that, when a treading forcefor the brake pedal 25 exceeds a specified value, a spring at the shockabsorber 35 operates not to transmit such excessive force to the brakelever 30.

A slide rod 35a (FIG. 6) in the shock absorber 35, one end of which isconnected to the bell crank 34, is inserted at the other end into acylinder 35c, in which a spring 35b is fitted onto the slide rod 35a andbiased in the compressing direction.

A cylinder rod 35d, which is fixed at one end to the cylinder 35c, ispivoted at the other end to the utmost end of a brake arm 37, and arotary base thereof is pivoted to a rotary shaft 40 fixed to a mountingplate 39 fixed onto the transmission case.

The brake arm 37 is biased toward the shock absorber 35 by a torsionspring 41 fitted onto the rotary shaft 40 and usually retained by astopper 38 projecting from the transmission case. A distance between thebrake arm 37 abutting against the stopper 38 and a regulator 42a biasedby the torsion spring 41 and positioned at the depth of a rotary groove44d during the speed change as shown in FIG. 6 is an allowance gap ofthe invention, through which the regulator 42a returns a speed changecam plate 44 to the neutral position in a time period when the regulator42a moves from the position in FIG. 6 to abut against the brake arm 37.

Also, a regulator arm 42 which is V-like-shaped, is pivoted at thecentral portion to the rotary shaft 40, at one utmost end of theregulator arm 42 is pivotally connected a brake link 43 connected withthe brake pedal 25, and the regulator 42a projects from the other end ofthe regulator arm 42 and is inserted into a regulation bore 44a open atone side of the speed change cam plate 44.

The speed change cam plate 44 is fixed at an intermediate portion to theswash plate angle control shaft 11 and provided at one side with theregulation bore 44d, 44c of a substantially T-like shape.

The regulation bore comprises the rotary groove 44d rotatable for thespeed change and formed in a circular arc around the swash plate controlshaft 11 and a rotary groove 44c for the braking action, into which theregulator 42a can enter when the variable swash plate 12 is in neutral,the grooves 44d and 44c being continuously integral with each other.

At the other end of the speed change cam plate 44 is pivoted a speedchange link 45 connected to a speed change operation unit 4 and includesguide bore 44b in a circular arc around the swash plate angle controlshaft 11, a neutral recess 44e (FIG. 6) is provided at the center ofguide bore 44b, and a neutral position biasing member 46a projectingfrom one end of an arm 46 is fitted into the guide bore 44b and biasedthereby. The arm 46 is pivoted at the other end to a pin 47 projectingfrom the mounting plate 39 and biased toward the swash plate anglecontrol shaft 11 by a spring 48 fitted onto the pin 47.

Accordingly, in the state shown in FIG. 4, the speed change cam plate 44and variable swash plate 12 are in the neutral positions respectively.

In the aforesaid construction, when the speed change control unit 4 isoperated in the state where the brake is not operated, that is, thebrake pedal 25 is not trod, as shown in FIG. 6, the speed change link 45rotates the speed change cam plate 44 in the direction of the arrow, theregulator 42a at the regulation arm 42 is positioned in the rotarygroove 44d for the speed changing so as not to regulate the rotation ofspeed change cam plate 44, and the speed change cam plate 44 is rotatedto rotate the swash plate angle control shaft 11, so that an angle ofthe variable swash plate 12 is changed and a discharge amount from thepiston 8 is changed, thereby changing the number of rotations of thehydraulic motor M.

On the other hand, in the neutral position biasing member 46a at the arm46 riding on the inclined surface of guide bore 44b is biased toward theswash plate angle control shaft 11, thereby being subjected to a forceby which the biasing member 46a rotates toward the neutral recess 44e atthe guide bore 44b with respect to speed change operation so as to beneutral.

Accordingly, when the speed change control unit 4 is released fromoperation, the neutral position biasing member 46a reversely rotates thespeed change cam plate 44, thereby returning it to the neutral position.

When the brake pedal 25 is trod in the starting condition, the brakelink 43 is pulled and the regulation arm 42 is rotated gradually fromthe position in FIG. 6, whereby the regulator 42a, as shown in FIG. 7,rotates from the rotary groove 44d for the speed changing to the rotarygroove 44c for the braking action, and the speed change cam plate 44rotates toward the neutral position following the rotation of regulator42a. Hence, the neutral position biasing member 46a holds the speedchange cam plate 44 in position.

Therefore, the variable swash plate 12 is put in the neutral positionand the hydraulic pump P generates no oil pressure, thereby cutting offa driving force of the hydraulic motor M.

Then, when the brake pedal 25 is trod, the allowance gap is consumed sothat the regulator 42a abuts against the brake arm 37 and rotates to thedepth of the rotary groove 44c, and the bell crank 34 rotates to pullthe brake link 33 while compressing the spring 35b at the shock absorber35, thereby turning the brake lever 30 for the braking action.

When an operator removes his foot from the brake pedal 25, a returnspring (not shown) reversely rotates the regulation arm 42 through thebrake link 43, thereby restoring the regulator 42a to the position shownin FIG. 4.

Next, explanation will be given on construction of a second embodimentof the invention shown in FIGS. 9 through 13.

In this embodiment, the association mechanism for the barke pedal 25with the speed change unit 4 is housed in the transmission case.

As shown in FIG. 9, however, the brake pedal 25 is connected to theupper portion of transmission case 1 through the brake link 43, and thespeed change operation unit 4 transmits the operating force to the uppersurface of transmission case 1, which is similar to the firstembodiment.

The brake link 43 is connected at the utmost end thereof to an arm 56which is fixed to a regulation arm 51 in the transmission case 1 throughthe rotary shaft 40.

The utmost end of speed change link 45 is connected to an arm 52projecting outwardly from the transmission case 1, the arm 52transmitting the operating force to the variable swash plate within thetransmission case 1 through the swash plate angle control shaft 11.

Next, explanation will be given on the state where the upper half case1a is removed from the transmission case 1 in accordance with the FIGS.10 and 11 of plan view.

In FIG. 11, the arm 52 is fixed to the swash plate angle control shaft11, and an arm 58 attached thereto rotates and is fitted at the utmostend into a recess at a variable swash plate engaging member 60 attachedto the side surface of the variable swash plate 12.

The swash plate angle control shaft 11 rotates so as to turn the arm 58,whereby the variable swash plate 12 is slid along the circular-arc guideto change an swash plate angle.

A speed change cam plate 50, other than the arm 58, is fixed to theswash plate angle control shaft 11 so as to be simultaneously rotatable.

At the speed change cam plate 50 are bored a rotary groove 50a for thebraking action and a rotary groove 50b for the speed changing, and atthe outer periphery of the cam plate 50 are provided an insertion recess50c for a neutral position holding ball 59 and inclined surfaces 50d atboth sides of the recess 50c. The neutral position holding ball 59 canadjust by a neutral position holding mechanism 57 from the exterior oftransmission case 1 the biasing force given to the speed change camplate 50.

The rotary groove 50a for the braking action and rotary groove 50b forthe speed changing communicate with each other to constitute aT-like-shaped cam groove, in which a regulator 51a at the utmost end ofthe regulation arm 51 is fitted.

The brake link 43 connected to the brake pedal 25 through the shockabsorber 23 is connected at the utmost end to the arm 56 which transmitsthe operating force into the transmission case 1 through the rotaryshaft 40, the regulation arm 51 being fixed to the lower end of therotary shaft 40.

The regulator 51a is fixed to the utmost end of regulation arm 51 and,as the above-mentioned, is inserted into the cam groove communicatingwith the rotary groove 50a for the braking action and rotary groove 50bfor the speed changing at the speed change cam plate 50.

It is required to provide at the regulation arm 51 an allowance gap forobtaining the allowance through which the speed change cam plate 50returns to the neutral position without starting the braking action ofthe braking device at first even when the brake pedal 25 is trod. Hence,in the second and third embodiments, the allowance gap is formed of anallowance elongate slot 51b provided at the regulation arm 51.

Into the allowance elongate slot 51b is inserted one end of a connectingrod 53 and the other end thereof is connected to an arm 54. The arm 54is fixed to a pivot shaft 36 and an arm 55 is fixed to part of the pivotshaft 36 projecting outwardly from the transmission case 1. A brake link33 is connected to the utmost end of arm 55 through the shock absorber35.

In this embodiment, an association mechanism for the braking device andspeed change apparatus is disposed within the transmission case 1 and,especially, the association mechanism is disposed at the reverse side tothe braking device beyond a power transmission mechanism constituted ofthe larger diameter gear 27 and differential ring gear 28, whereby it isrequired to provide a space through which the connecting rod 53 from theassociation mechanism to the braking device passes.

The connecting rod 53 is pushed or pulled together with operation ofbrake pedal 25 so as to turn somewhat longitudinally, thereby requiringa sufficient gap.

In the present invention, the connecting rod 53 passes through a spacebetween a counter shaft bearing 32 for supporting a counter shaft 26a atthe power transmission mechanism and the axle bearing 49 for supportingthe axles 13.

Also, as shown in FIG. 13 and FIG. 15 showing a third embodiment of theinvention, when the association mechanism for the braking device andspeed change apparatus is disposed in the transmission case 1, themechanism is hung to be supported to shafts projected from the upperhalf case 1a.

Accordingly, the state shown in FIG. 10 cannot actually exist, but forthe convenience of explanation the association mechanism only is shownupwardly of the lower half case 1b.

In addition, operation of the speed change cam plate 50 by the speedchange operation unit 4 and that of the speed change cam plate 5 duringthe operation of brake pedal 25 are omitted as they are the same in thefirst embodiment.

The second embodiment is different from the first embodiment in that theneutral holding mechanism and shock absorber 35 are different inposition and the association mechanism is disposed in the transmissioncase 1, but similar to the first embodiment in that, when the brakepedal 25 is operated, the variable swash plate 12 is forcibly returnedto the neutral position.

Next, explanation will be given on construction of the third embodimentin accordance with FIGS. 14 and 15.

In the third embodiment, as in the second embodiment, the associationmechanism for the braking device and speed change apparatus is disposedwithin the transmission case 1, but an operation mechanism for thevariable swash plate 12 is improved.

In other words, the second and third embodiments are similar in that arotary groove 62a for the braking action and a rotary groove 62c for thespeed changing are open at a speed change cam plate 62 in condition ofcommunicating with each other, a regulator 51a at a regulation arm 51 isfitted into the communicating grooves so that, when the brake pedal 25is trod and the regulator 51a enters into the rotary groove 62a, thevariable swash plate 12 is returned to the neutral position through thespeed change cam plate 62. However, a swash plate operating cam groove62b is bored in addition to the speed change cam plate 62.

The speed change cam plate 62 is connected through a rotary shaft 68with the arm 52 linked with the speed change operating unit 4 and aswash plate operating member 63a for an arm 63 fixed to the swash plateangle control shaft 11 is inserted into the swash plate operating groove62b. In this case, the third embodiment is different from the firstsecond embodiments in that the rotation of speed change cam plate 62 isnot transmitted directly to the swash plate angle control shaft 11.

The swash plate operating cam groove 62b is so formed that the variableswash plate 12, when the speed change operation unit 4 is operated invicinity of the neutral, is rotated merely slowly, and largely at theposition apart from neutral.

The swash plate angle control shaft 11, as shown in FIG. 15, issupported rotatably to a pivot portion 11b at a neutral adjusting shaft11a and the neutral adjusting shaft 11a and pivot portion 11b are formedto be somewhat eccentric so that the neutral adjusting shaft 11a isproperly rotated and fixed, and the swash plate angle control shaft 11shifts in position, thereby enabling the neutral position of thevariable swash plate 12 to be set with accuracy.

Also, in the second embodiment, in order to hold the speed change camplate 62 in the neutral position, the neutral holding ball 59 projectsoutwardly from the transmission case 1 so as to be biased and fittedinto the neutral position ball insertion groove, but in the thirdembodiment, the neutral holding mechanism is constituted within thetransmission case 1.

In other words, a neutral holding arm 64 is integrally pivoted by apivot shaft 64a and a neutral position biasing member 64b provided atthe neutral holding arm 64 is adapted to be permanently biased to abutagainst the neutral position holding recess 62d at the speed change camplate 62 by permanently biasing springs 66 and 65 (FIG. 16). Referencenumeral 67 designates a support for blocking movement of eachpermanently biasing spring 66 or 65.

A permanently biasing spring 66 is attached to one end of a biasing rod65 through a spring holder and the other end of the same is attached toa wall of the upper half case 1a through a spring holder. Accordingly,when the speed change cam plate 62 rotates to the speed change position,the neutral position biasing member 64b rides on an inclined surface62e, the neutral holding arm 64 rotates together with the pivot shaft64a to pull the biasing rod 65, thereby compressing the permanentlybiasing spring 66. Hence, the permanently biasing spring 66 gives theinverted biasing rotation force to the neutral holding arm 64 so thatthe speed change cam plate 62 is subjected to a force for fitting theneutral position biasing member 64b into the neutral position holdingrecess 62d.

As shown in FIG. 15, an arm 69 is provided at part of pivot shaft 64aprojecting from the transmission case 1 so that, when the pivot shaft64a is rotated as above-mentioned, a neutral position detecting switch70 is adapted to be off.

The third embodiment is different from the first embodiment in therotation mechanism for the neutral holding mechanism or the variableswash plate 12, but similar to the same in operation of returning thevariable swash plate 12 to the neutral position by operating the brakepedal 25.

Next, the effect of the present invention will be described withreference to construction to be claimed as follows:

The variable swash plate 12 at the variable displacement hydraulic pumpP is first returned to the neutral position while the allowance gapprovided between the link and the arm is being operated during theoperation of brake operating unit, and thereafter the braking deviceexerts the braking action, whereby the hydraulic pump P and hydraulicmotor M are not subjected to an overload and also the engine E is notsubjected thereto, resulting in that the engine does not stop occurs.

Also, the regulator 42a rotates and shifts while holding the speedchange cam plate 44 in the neutral position and the brake arm 37 andlink are operated to actuate the braking device and the speed change camplate 44 is kept stable in the neutral position by the regulator 42a forthe braking action, thereby enabling the hydraulic pump P or hydraulicmotor M to be prevented from a breakdown.

The speed change cam plate 44 is formed in a flat plate and the rotarygroove 44d for the speed changing and the rotary groove 44c for thebraking action are constituted so that the association mechanism can besmaller in thickness when viewed from the lateral side, thereby enablingthe apparatus to be compact.

When the regulator 42a returns the speed change cam plate 44 to theneutral position, the neutral mechanism biases the speed change camplate 44 toward the neutral position, thereby enabling the return timeto be quicker. Also, since the speed change cam plate 44 can reliably befixed in the neutral position, even when the brake operating unit isabruptly operated in the emergency braking action, the swash plate 12can reliably be held in the neutral position.

An excessive braking force is cut by the shock absorber 35 interposedbetween the regulation arm and the break lever, thereby protecting ofthe braking device.

Since the association mechanism for the braking device and variableswash plate is disposed in the transmission case 1, part of theassociation mechanism can be lubricated by lubricating oil within thetransmission case and be prevented from rusting or mudding, therebyenabling a stable operation.

Since the association mechanism for the braking device and variableswash plate is disposed in a dead space at the HST type speed changeapparatus, the transmission case 1 can be compact.

The association mechanism for the braking device and swash plate issupported at the upper half casing 1a, thereby being simple to assemble.

The association mechanism is disposed in a space at the HST type speedchange apparatus and the connection rod 53, which transmits theoperating force to the braking device disposed at the reverse side tothe association mechanism beyond the power transmission mechanism, canbe pushed or pulled smoothly without any hindrance.

Although several embodiments have been described, they are merelyexemplary of the invention and not to be constructed as limiting, theinvention being defined solely by the appended claims.

What is claimed is:
 1. Apparatus for selectively braking rotation of adriving axle driven by a hydraulic transmission, comprising:a speedchange operation unit for shifting operation of the hydraulictransmission between an operative position wherein the hydraulictransmission transmits a driving power to the axle, and a neutralposition wherein no power is transmitted by said hydraulic transmissionto said axle; a speed change cam plate pivotably connected to said speedchange operation unit, said speed change cam plate forming an allowancegap, said allowance gap including a first rotary groove and a secondrotary groove; a brake operation link pivotably connected at one end ofa regulation arm; a cam follower disposed at another end of saidregulation arm, said cam follower received within said allowance gap ofsaid speed change cam plate; wherein, when said hydraulic transmissionis in the operative position, said cam follower is received within saidfirst rotary groove of said allowance gap; and wherein, when force isapplied to said brake operation link, said hydraulic transmission isshifted to the neutral position and said cam follower is received withinsaid second rotary groove of said allowance gap before braking of therotation of said driving axle is commenced.
 2. Apparatus for selectivelybraking rotation of a driving axle driven by a hydraulic transmission asset forth in claim 1, further comprising:a brake lever for actuating abraking device for braking rotation of said axle; a shock absorberdisposed between said regulation arm and said brake lever.
 3. An axledriving apparatus, comprising:a transmission casing for supporting anaxle; a hydraulic pump disposed within said transmission casingincluding a swash plate; a swash plate angle control shaft operativelyconnected to said swash plate for altering the rotation of saidhydraulic pump between an operative position and a neutral position; ahydraulic motor disposed within said transmission casing and driven bysaid hydraulic pump to constitute a power transmission; a speed changecam plate fixed to said swash plate angle control shaft disposed withinsaid transmission casing, said speed change cam plate including a rotarygroove; a speed change link for rotating said speed change cam plate; abraking device for selectively braking rotation of said axle, saidbraking device including a regulation arm disposed within saidtransmission casing and rotatably by a brake link connected to a brakepedal; and a regulator disposed at one end of said regulation arm andreceived within said rotary groove of said speed change cam plate.
 4. Anaxle driving apparatus as set forth in claim 3, wherein saidtransmission casing is divided horizontally with respect to said axleinto an upper portion and a lower portion, and wherein said upper andlower portions pivotally support said axle within a bearing, saidassociation mechanism being disposed along said upper portion.
 5. Anaxle driving apparatus as set forth in claim 4, wherein said connectingrod extends from said association mechanism to said braking device andis disposed between said axle bearing and said power transmission.
 6. Anaxle driving apparatus as set forth in claim 3, further comprising:anassociation mechanism disposed outside said transmission casing foroperating said braking device; a connecting rod disposed within saidtransmission casing connected to said association mechanism; and anallowance gap formed in said regulation arm, wherein an end of saidconnecting rod is received within said allowance gap.